The Intelligent Network (IN) is an architectural concept that enables real-time execution of network services and customer applications in a distributed environment of interconnected computers and switching systems, such as wireline and wireless telephone networks. IN standards have been promulgated by the International Telecommunications Union (ITU-T) and by the American National Standards Institute (ANSI). A useful summary of IN concepts and standards is provided by Faynberg et al., in “The Development of the Wireless Intelligent Network (WIN) and Its Relation to the International Intelligent Network Standards”, Bell Labs Technical Journal (Summer, 1997), pp. 57-80, which is incorporated herein by reference.
FIG. 1 is a block diagram that schematically illustrates a cellular telephone network 20 that is configured for provision of IN services, as is known in the art. A cellular telephone 22 communicates with the network via a base station controller (BSC) 24, which is coupled to a mobile switching center (MSC) 26. Although for the sake of simplicity, only a single BSC and MSC are shown in the figure, typical cellular networks comprise multiple BSCs, MSCs and other elements. MSC 26 serves as a switch, receiving signaling and voice communications from telephone 22 via BSC 24, and transferring the communications to other network elements in order to complete and carry out calls made by or to telephone 22. The BSC, MSC and other elements of the cellular network are connected by a public land mobile network (PLMN) 28, which typically operates in accordance with the well-known Signaling System 7 (SS-7) protocol.
In order to provide IN services, MSC 26 is programmed with a call control function (CCF) 30 and a service switching function (SSF) 32, as dictated by IN standards. The CCF provides basic switching capabilities, including the means to establish, manipulate and release calls and connections. When the CCF detects signaling passing through the MSC that is related to an IN service, it suspends the call temporarily and passes a trigger to the SSF. Based on the trigger, SSF 32 passes control of the call to a service control point (SCP) 34. While CCF 30 and SSF 32 are implemented in the network switches themselves, SCP 34 is typically a separate element, which communicates with the network switches over the SS7 network. Communications between SSF 32 and SCP 34 are based on a standard IN Application Protocol (INAP). The SCP processes the call, and then sends instructions back via INAP to SSF 32 as to how the call should be handled by CCF 30.
As will be appreciated from FIG. 1, the basic idea of IN is to move intelligent services out of the network switches to separate service points, such as SCP 34. Multiple SCPs may communicate with a given switch. SSF 32 of the switch is programmed to choose the SCP for each call depending on the trigger parameters. By the same token, a single SCP can communicate with and service multiple switches (although not all the switches in a network are necessarily IN-enabled). The unified IN architecture allows different service providers to create SCPs that implement their own particular services, independent of the underlying network technology.
For example, assuming SCP 34 is responsible for provision of an 800-number service, the CCF/SSF will suspend and refer 800-number calls to the SCP, which analyzes the calls using its own service logic and then returns instructions to the SSF. These instructions would typically cause MSC 26 to reroute the call to an ordinary subscriber number of the call recipient, while charging the recipient for the call if appropriate. On the other hand, the SCP might instruct the SSF/CCF to transfer the call to an intelligent peripheral (IP) 36. Typical IP functions include playing prerecorded or synthesized voice responses, or capturing Dual Tone Multi-Frequency (DTMF) input from the keypad of telephone 22. These IP functions are usually controlled by commands from the SCP, which then instructs the SSF/CCF as to how the call should proceed. Although the example shown in FIG. 1 relates to wireless network 20, the principles embodied in this example relate to wireline networks, as well.
Introducing IN services in a non-IN-enabled network requires local exchange switches to be replaced or at least reprogrammed to provide the necessary CCF/SSF functionality, as well as to upgrade this functionality in response to changes in the IN standard and required capabilities. (For example, the original IN standard capability set, CS-1, was supplemented in 1997 to define a much richer and broader set. CS-2, and further changes of this sort can be expected in the future.) In cellular networks, where a given subscriber can be expected to connect from any point to any point in the network, any upgrade must be implemented on all of the switches in the network, at very substantial cost. This cost is a serious hindrance to the introduction of new and enhanced IN functionalities.